1. Field of the Invention
The present invention relates to a display element having a fine periodic structure. For example, the present invention relates to a display device or an image observation system that displays an image by modulating light beam from a light source for every pixel.
2. Related Background Art
Self light emitting display devices such as PDPs, EL displays, and FEDs, and light bulb type display devices such as an LCD in which a back light and a space modulation element are combined together are known as conventional flat panel display devices. The display devices still have a lot of room for improvement, however, in their size, electric power consumption, display image contrast, moving image display characteristics, and the like. On the other hand, use of a display that guides light from a light source means to an optical fiber, extracts the light from the optical fiber for each pixel through a liquid crystal switch, and uses the light to excite a fluorescent substance to effect display has been proposed (Japanese Patent Application Laid-open No. 2001-51271) as a method for achieving saving of space, saving of electric power, and high image quality. Further, a two dimensional photonic crystal waveguide is known (U.S. Patent Application Publication No. 2002/009277). A linear and point defect is formed within a two dimensional photonic crystal having a refractive index with a two dimensional periodic distribution, thus forming a waveguide within the two dimensional photonic crystal. The light and electromagnetic waves propagating through the waveguide are guided in a direction perpendicular to surface.
In the display disclosed in Japanese Patent Application Laid-open No. 2001-51271, since light is extracted by breaking down the total internal reflection conditions of the optical fiber by change in refractive index of the crystal, it is difficult to locally change the refractive index. The extracted light thus expands without directionality, and cannot efficiently excite the fluorescent substances. Furthermore, light easily leaks out to adjacent pixels, and the image quality tends to decrease.
U.S. Patent Application Publication No. 2002/009277 discloses making light having a plurality of wavelengths incident into a two dimensional photonic crystalline waveguide, and guiding light having a predetermined wavelength, among all of the light propagating in the two dimensional photonic crystalline waveguide, in a direction perpendicular to surface (see FIG. 16). However, the refractive index of the two dimensional photonic crystalline structure provided with the refractive index distribution is not controlled so as to control light emission.
U.S. Patent Application Publication No. 2002/159733 discloses that light having a predetermined wavelength that coincides with a resonant wavelength of a resonator among all light propagating in a two dimensional photonic crystalline waveguide, is reflected so that the reflected light propagates in a direction opposite to the direction in which the light had been propagating, and the refractive index distribution of the resonator is changed so as to control the wavelength to be reflected. However, it does not disclose guiding the light propagating within the waveguide in a direction perpendicular to surface.